No other exercise matches running for its ability to soak that sports bra. The stair-stepper, bike, and other gym staples work you hard, but running blasts the most calories: In a study done by the Medical College of Wisconsin and the VA Medical Center, the treadmill (used at a "hard" exertion level) torched an average of 705-865 calories in an hour. The stair-stepper (637-746), rower (606-739), cross-country ski machine (595-678) and stationary bike (498-604) were all lower in overall caloric burn.

Running also gives your ticker a world-class workout. When your legs hit their stride they squeeze blood toward your heart, which in turn forces it to pump the blood right back. The faster you run, the harder your heart works and the stronger it gets.

Contrary to what your mom says, running doesn't wreck your joints. Osteoarthritis (the most common type of arthritis), occurs when joint-cushioning cartilage starts to break down. The biggest osteoarthritis risk factor besides age? Body weight. A National Health and Nutrition Examination Survey found that obese women had nearly four times the risk of knee osteoarthritis than non-obese women; for men, it was five times the risk. Runners are much more likely to be at a normal weight than members of the sedentary population, significantly decreasing their risk of osteoarthritis.

It goes further than just the benefits of weight loss, too. Running bolsters your cartilage by increasing oxygen flow and flushing out toxins, and by strengthening the ligaments around your joints. Hitting the trail also gives your bones a boost, helping to prevent osteoporosis.

Though it's important to treat all running injuries and to replace your shoes often, in the end, running will build your joints up, not tear them down.

Runners can provide tons of anecdotes about the stress-busting powers of their regular jog. "Nothing beats that feeling when you settle into a strong stride with a powerful rhythm," says Brooke Stevens, a four-time NYC marathoner, "The tension in my neck, back, and shoulders starts to loosen up, and I can think more clearly too."

Many women swear they work out all of their problems on the road, and there's research on exercise to back them up. The University of Georgia Department of Exercise induced anxiety (no worries, it was with caffeine pills) on subjects and then tested their physiological and mood symptoms after either resting for an hour or exercising for that hour. The exercise (in this case, on a stationary bike), was three times more effective at reducing anxiety.

Running is even used by mental health experts to help treat clinical depression and other psychological disorders such as drug and alcohol addiction.

Most experts agree that regular exercise reduces the risk of many kinds of cancer, including some of the scariest: colon, breast, endometrial, and lung. One recent study in the British Journal of Cancer calculated that the "most active" (e.g. walked briskly 5-6 hours/week) people were 24 percent less likely to develop colon cancer than the "least active" people (e.g. 30 minutes of walking/week). In a study by the National Cancer Institute, women of a normal weight who reported the highest levels of "vigorous activity" (running, tennis, aerobics) had about a 30 percent lower risk of breast cancer when compared with women who did no vigorous activity. Becoming a regular runner may help you cancer-proof your life.

Joggers also have a leg up against heart disease, stroke, and diabetes, and running has been shown to lower blood pressure, raise good cholesterol, and boost immunity to colds and other viruses.

Your time on the treadmill can even prevent vision loss, it seems. Two studies from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have found that running reduced the risk of age-related macular degeneration and cataracts.

In perhaps the most surprising study done on the health benefits of running, a team at the Stanford University School of Medicine studied 538 runners and 423 healthy non-runners from 1984 until 2005. All of the subjects were over 50 and were asked to take a disability questionnaire each year measuring simple tasks like cutting meat, shampooing hair, and opening a milk carton.

Every year, the disability levels were significantly lower in the group of runners than in the non-runners, and they became more different as both groups aged.

Even more interesting (though admittedly morbid)? At the end of the study, 85 percent of the runners were still alive, while only 66 percent of the non-runners were.

Based on the info gathered during the 21 years, the researchers concluded that regular exercise could reduce both disability and risk of death by increasing cardio fitness and bone mass, lowering inflammation, improving response to vaccination, and improving thinking, learning, and memory functions. We say, is that all?